A post shared by Khloé (@khloekardashian) on Dec 20, 2017 at 2:41pm PST

Kardashian is the younger sister of Kim Kardashian West. Thompson plays is a center-forward with the Cleveland Cavaliers.

The couple's pregnancy had been rumored for months. Khloe Kardashian said in her post Wednesday that they intentionally kept the news quiet so they could "enjoy this between our family and close friends as long as we could privately."